Nowadays metallic water meter casings are all molded by one piece casting of the prior art because of their relatively complicated structures. This kind of casting technique of molding by one piece casting may result in that the wall of the water meter casing is very thick and that the cost for casting is relatively high, thereby leading to a relatively high cost of production for the metallic water meter casing. Moreover, derivatives which are harmful to the human body may be generated during the process of one piece casting, or there may be certain substances required to be added for products molding which are mostly harmful to the human body.